GCSE BIOLOGY AQA
Paper 1
Topics 1-4
1. Cell biology
2. Organisation
3. Infection and response
4. Bioenergetics
1hour 45 minutes
100 marks
50% of GCSE
,TOPIC 1: CELL BIOLOGY
All living things are made of cells
EUKARYOTES AND PROKARYOTES
Eukaryotes = animal and plant cells
Prokaryotes = bacteria cells
Eukaryotic cells contain their genetic material enclosed in a nucleus.
Prokaryotic cells have a singular loop of DNA instead.
Prokaryotic cells are much smaller than eukaryotic cells.
SIZES OF CELLS
▪ ‘Centi’ means 1/100th, so 1cm is 1/100th of a metre
1cm = 1 x 10-2
▪ ‘Milli’ means 1/1000th, so 1mm is 1/1000th of a metre
1mm= 1 x 10-3
▪ ‘Micro’ means 1/1000000th, so 1μm is 1/1000000th of a metre
1 μm= 1 x 106
Typical human cell= 10-20μm
ORDER OF MAGNITUDE
Every order of magnitude is 10x greater than the one before
10x= one order of magnitude
100x= two orders of magnitude
1000x= three orders of magnitude
ANIMAL CELLS: EUKARYOTES
▪ Nucleus- controls the cell as contains the genetic material
▪ Ribosomes- sites of protein-synthesis
▪ Mitochondria- store of energy for aerobic respiration to take place
▪ Cytoplasm- where chemical reactions take place
▪ Cell membrane- controls the molecules that can enter and leave the
cell
,PLANT CELLS: EUKARYOTES
▪ Nucleus- controls the cell as contains the genetic material
▪ Ribosomes- sites of protein-synthesis
▪ Mitochondria- store of energy for aerobic respiration
▪ Cytoplasm- where chemical reactions take place
▪ Vacuole- contains cells sap which gives cell shape
▪ Cell wall- contains cellulose which strengthens cell
▪ Cell membrane- controls the molecules that can enter and
leave the cell
▪ Chloroplasts-contain chlorophyll and are the sites of
photosynthesis
BACTERIAL CELLS: PROKARYOTES
▪ Cytoplasm- where chemical reactions take place
▪ Cell wall- contains cell sap which strengthens cell
▪ DNA- contains genetic information (controls cell)
▪ Plasmids- small rings of additional DNA
▪ Cell membrane- controls the molecules that can enter and leave the
cell
MICROSCOPY
Microscopes allows us to magnify
Light microscopes have a limited magnification and resolution
Light microscopes are used to see larger subcellular substances
Electron microscopes=
✓ Clearer resolution
✓ Greater magnification
✓ Can see between subcellular substances (ribosomes and mitochondria)
IMAGE SIZE= ACTUAL SIZE X MAGNIFICATION
‘mm’ X1000 micrometres
micrometres / 1000 ‘mm’
, CELL SPECIALISATION AND DIFFERENTIATION
Cell Differentiation is the process by which a cell changes to become specialised for its job
• Most animal and plant cells are specialised
• Animal cells differentiate at an early stage
• Plant cells differentiate throughout their life
Animal cells
1. Muscle cells- adapted for contraction by having long cells. Also, they contain many mitochondria to
generate energy needed. The protein fibres can change their length.
2. Sperm cells -adapted for reproduction by having a long tail and a streamlined head to help swim to egg.
The many mitochondria provide energy needed for swimming. The enzymes allow the cells to digest
through the outer layer of the ovum.
3. Nerve cells- adapted for rapid signalling by having long cells with branched connections at each end to
form a network throughout the body.
Plant cells
1. Root hair cells- adapted for absorbing water and minerals by having long hairs to increase the surface
area. Do not contain chloroplasts.
2. Phloem cells- adapted for transporting dissolved sugars by not having a nucleus and only having limited
cytoplasm so that food can flow easily. The end walls of the cells have pores called sieve plates; they
allow dissolved sugars to move through the interior of the cell. Each phloem vessel cell has a
companion cell which has mitochondria to provide energy.
3. Xylem cells- adapted for transporting water by having very thick walls containing lignin to provide
support. No nucleus, cytoplasm, vacuole, or chloroplasts so that water and minerals can flow easily.
Paper 1
Topics 1-4
1. Cell biology
2. Organisation
3. Infection and response
4. Bioenergetics
1hour 45 minutes
100 marks
50% of GCSE
,TOPIC 1: CELL BIOLOGY
All living things are made of cells
EUKARYOTES AND PROKARYOTES
Eukaryotes = animal and plant cells
Prokaryotes = bacteria cells
Eukaryotic cells contain their genetic material enclosed in a nucleus.
Prokaryotic cells have a singular loop of DNA instead.
Prokaryotic cells are much smaller than eukaryotic cells.
SIZES OF CELLS
▪ ‘Centi’ means 1/100th, so 1cm is 1/100th of a metre
1cm = 1 x 10-2
▪ ‘Milli’ means 1/1000th, so 1mm is 1/1000th of a metre
1mm= 1 x 10-3
▪ ‘Micro’ means 1/1000000th, so 1μm is 1/1000000th of a metre
1 μm= 1 x 106
Typical human cell= 10-20μm
ORDER OF MAGNITUDE
Every order of magnitude is 10x greater than the one before
10x= one order of magnitude
100x= two orders of magnitude
1000x= three orders of magnitude
ANIMAL CELLS: EUKARYOTES
▪ Nucleus- controls the cell as contains the genetic material
▪ Ribosomes- sites of protein-synthesis
▪ Mitochondria- store of energy for aerobic respiration to take place
▪ Cytoplasm- where chemical reactions take place
▪ Cell membrane- controls the molecules that can enter and leave the
cell
,PLANT CELLS: EUKARYOTES
▪ Nucleus- controls the cell as contains the genetic material
▪ Ribosomes- sites of protein-synthesis
▪ Mitochondria- store of energy for aerobic respiration
▪ Cytoplasm- where chemical reactions take place
▪ Vacuole- contains cells sap which gives cell shape
▪ Cell wall- contains cellulose which strengthens cell
▪ Cell membrane- controls the molecules that can enter and
leave the cell
▪ Chloroplasts-contain chlorophyll and are the sites of
photosynthesis
BACTERIAL CELLS: PROKARYOTES
▪ Cytoplasm- where chemical reactions take place
▪ Cell wall- contains cell sap which strengthens cell
▪ DNA- contains genetic information (controls cell)
▪ Plasmids- small rings of additional DNA
▪ Cell membrane- controls the molecules that can enter and leave the
cell
MICROSCOPY
Microscopes allows us to magnify
Light microscopes have a limited magnification and resolution
Light microscopes are used to see larger subcellular substances
Electron microscopes=
✓ Clearer resolution
✓ Greater magnification
✓ Can see between subcellular substances (ribosomes and mitochondria)
IMAGE SIZE= ACTUAL SIZE X MAGNIFICATION
‘mm’ X1000 micrometres
micrometres / 1000 ‘mm’
, CELL SPECIALISATION AND DIFFERENTIATION
Cell Differentiation is the process by which a cell changes to become specialised for its job
• Most animal and plant cells are specialised
• Animal cells differentiate at an early stage
• Plant cells differentiate throughout their life
Animal cells
1. Muscle cells- adapted for contraction by having long cells. Also, they contain many mitochondria to
generate energy needed. The protein fibres can change their length.
2. Sperm cells -adapted for reproduction by having a long tail and a streamlined head to help swim to egg.
The many mitochondria provide energy needed for swimming. The enzymes allow the cells to digest
through the outer layer of the ovum.
3. Nerve cells- adapted for rapid signalling by having long cells with branched connections at each end to
form a network throughout the body.
Plant cells
1. Root hair cells- adapted for absorbing water and minerals by having long hairs to increase the surface
area. Do not contain chloroplasts.
2. Phloem cells- adapted for transporting dissolved sugars by not having a nucleus and only having limited
cytoplasm so that food can flow easily. The end walls of the cells have pores called sieve plates; they
allow dissolved sugars to move through the interior of the cell. Each phloem vessel cell has a
companion cell which has mitochondria to provide energy.
3. Xylem cells- adapted for transporting water by having very thick walls containing lignin to provide
support. No nucleus, cytoplasm, vacuole, or chloroplasts so that water and minerals can flow easily.
